The opioid receptors were identified in the mid-1970's, and were quickly categorized into three sub-sets of receptors (mu, delta and kappa). More recently the original three types of receptors have been further divided into sub-types. Also known is that the family of opioid receptors are members of the G-protein coupled receptor (GPCR) super-family More physiologically pertinent are the well established facts that opioid receptors are found throughout the central and peripheral nervous system of many mammalian species, including humans, and that modulation of the respective receptors can elicit numerous, albeit different, biological effects, both desirable and undesirable (D. S. Fries, “Analgesics”, in Principles of Medicinal Chemistry, 4th ed.; W. O. Foye, T. L. Lemke, and D. A. Williams, Eds.; Williams and Wilkins: Baltimore, Md., 1995; pp. 247–269; J. V. Aldrich, “Analgesics”, Burger's Medicinal Chemistry and Drug Discovery, 5th Edition, Volume 3: Therapeutic Agents, John Wiley & Sons, Inc., 1996, pp. 321–441). In the most current literature, the likelihood of heterodimerization of the sub-classes of opioid receptors has been reported, with respective physiological responses yet undetermined (Pierre J. M. Riviere and Jean-Louis Junien, “Opioid receptors: Targets for new gastrointestinal drug development”, Drug Development 2000, pp. 203–238).
A couple biological effects identified for opioid modulators have led to many useful medicinal agents. Most significant are the many centrally acting mu opioid agonist modulators marketed as analgesic agents to attenuate pain (e.g., morphine), as well as peripherally acting mu agonists to regulate motility (e.g., loperamide). Currently, clinical studies are continuing to evaluate medicinal utility of selective delta, mu, and kappa modulators, as well as compounds possessing combined sub-type modulation. It is envisioned such explorations may lead to agents with new utilities, or agents with minimized adverse side effects relative to currently available agents (examples of side effects for morphine includes constipation, respiratory depression, and addiction potential). Some new GI areas where selective or mixed opioid modulators are currently being evaluated includes potential treatment for various diarrheic syndromes, motility disorders (post-operative ileus, constipation), and visceral pain (post operative pain, irritable bowel syndrome, and inflammatory bowel disorders) (Pierre J. M. Riviere and Jean-Louis Junien, “Opioid receptors: Targets for new gastrointestinal drug development” Drug Development, 2000, pp. 203–238).
Around the same time the opioid receptors were identified, the enkephalins were identified as a set of endogenous opioid ligands (D. S. Fries, “Analgesics”, in Principles of Medicinal Chemistry, 4th ed.; W. O. Foye; T. L. Lemke, and D. A. Williams, Eds.; Williams and Wilkins: Baltimore, Md., 1995; pp. 247–269). Schiller discovered that truncating the original pentapeptide enkephalins to simplified dipeptides yielded a series of compounds that maintained opioid activity (Schiller, P. WO 96/06855). However one potential drawback cited for such compounds is the likelihood of their inherent instability (P. W. Schiller et al., Int. J. Pept. Protein Res. 1993, 41 (3), pp. 313–316).
More recently, a series of opioid pseudopeptides containing heteroaromatic or heteroaliphatic nuclei were disclosed, however this series is reported showing a different functional profile than that described in the Schiller works. (L. H. Lazarus et al., Peptides 2000, 21, pp. 1663–1671)
Most recently, works around morphine related structures were reported by Wentland, et al, where carboxamido derivatives morphine and it's analogs were prepared (M. P. Wentland et al., Biorg. Med. Chem. Letters 2001, 11, pp. 1717–1721; M. P. Wentland et al., Biorg. Med. Chem. Letters 2001, 11, pp. 623–626). Wentland found that substitution for the phenol moiety of the morphine related structures with a primary carboxamide led anywhere from equal activities up to 40 fold reduced activities, depending on the opioid receptor and the carboxamide. It was also revealed that any additional N-substitutions on the carboxamide significantly diminished the desired binding activity.
Compounds of the present invention have not been previously disclosed and are believed to provide advantages over related compounds by providing improved pharmacological profiles.
It is expected that opioid receptor modulators, agonists or antagonists may be useful in the treatment and prevention of various mammalian disease states, for example pain and gastrointestinal disorders such as diarrheic syndromes, motility disorders including post-operative ileus and constipation, and visceral pain including post-operative pain, irritable bowel syndrome and inflammatory bowel disorders.
It is an object of the present invention to provide opioid receptor modulators. It is a further object of the invention to provide opioid receptor agonists and opioid receptor antagonists. It is an object of the present invention to provide opioid receptor ligands that are selective for each type of opioid receptor, mu, delta and kappa. It is a further object of the present invention to provide opioid receptor ligands that modulate two or three opioid receptor types, mu, delta and kappa, simultaneously. It is an object of the invention to provide certain instant compounds that are also useful as intermediates in preparing new opioid receptor modulators. It is also an object of the invention to provide a method of treating or ameliorating a condition mediated by an opioid receptor. And, it is an object of the invention to provide a useful pharmaceutical composition comprising a compound of the present invention useful as an opioid receptor modulator.